/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.hudi.common.util.collection;

import org.apache.hudi.common.engine.HoodieReaderContext;

public abstract class CachingIterator<T> implements ClosableIterator<T> {

  protected T nextRecord;

  protected abstract boolean doHasNext();

  @Override
  public final boolean hasNext() {
    return nextRecord != null || doHasNext();
  }

  @Override
  public final T next() {
    T record = nextRecord;
    nextRecord = null;
    return record;
  }

  public static <U> CachingIterator<U> wrap(ClosableIterator<U> iterator) {
    return new CachingIterator<U>() {
      @Override
      protected boolean doHasNext() {
        if (iterator.hasNext()) {
          nextRecord = iterator.next();
          return true;
        }
        return false;
      }

      @Override
      public void close() {
        iterator.close();
      }
    };
  }

  public static <U> CachingIterator<U> wrap(ClosableIterator<U> iterator, HoodieReaderContext<U> readerContext) {
    return new CachingIterator<U>() {
      @Override
      protected boolean doHasNext() {
        if (iterator.hasNext()) {
          nextRecord = readerContext.seal(iterator.next());
          return true;
        }
        return false;
      }

      @Override
      public void close() {
        iterator.close();
      }
    };
  }

}
